Happy Bit Setting In A mobile Communication System

ABSTRACT

The invention relates to a mobile terminal communicating resource requests for dedicated uplink channel resources in a mobile communication system. Further, the invention also relates to a method for communicating resource requests for dedicated uplink channel resources in a mobile communication system. To allow the serving cell to detect “DOWN” commands from non-serving cells during soft handover the invention suggests a new definition of criteria for setting the “happy bit” in the control information associated to data transmitted on dedicated uplink channels. According to these criteria the mobile terminal may not indicate an unhappy condition while ramping up resource utilization. Only if resources equivalent to the maximum serving grant are utilized, the transmission buffer status requires to and the power status of the terminal allows for the happy bit is set to indicate a unhappy condition.

FIELD OF THE INVENTION

The invention relates to a mobile terminal communicating resourcerequests for dedicated uplink channel resources in a mobilecommunication system. Further, the invention also relates to a methodfor communicating resource requests for dedicated uplink channelresources in a mobile communication system.

TECHNICAL BACKGROUND

W-CDMA (Wideband Code Division Multiple Access) is a radio interface forIMT-2000 (International Mobile Communication), which was standardizedfor use as the 3^(rd) generation wireless mobile telecommunicationsystem. It provides a variety of services such as voice services andmultimedia mobile communication services in a flexible and efficientway. The standardization bodies in Japan, Europe, USA, and othercountries have jointly organized a project called the 3^(rd) GenerationPartnership Project (3GPP) to produce common radio interfacespecifications for W-CDMA.

The standardized European version of IMT-2000 is commonly called UMTS(Universal Mobile Telecommunication System). The first release of thespecification of UMTS has been published in 1999 (Release 99). In themean time several improvements to the standard have been standardized bythe 3GPP in Release 4 and Release 5 and discussion on furtherimprovements is ongoing under the scope of Release 6.

The dedicated channel (DCH) for downlink and uplink and the downlinkshared channel (DSCH) have been defined in Release 99 and Release 4. Inthe following years, the developers recognized that for providingmultimedia services—or data services in general—high speed asymmetricaccess had to be implemented. In Release 5 the high-speed downlinkpacket access (HSDPA) was introduced. The new high-speed downlink sharedchannel (HS-DSCH) provides downlink high-speed access to the user fromthe UMTS Radio Access Network (RAN) to the communication terminals,called user equipments in the UMTS specifications.

Hybrid ARQ Schemes

A common technique for error detection and correction in packettransmission systems over unreliable channels is called hybrid AutomaticRepeat request (HARQ). Hybrid ARQ is a combination of Forward ErrorCorrection (FEC) and ARQ.

If a FEC encoded packet is transmitted and the receiver fails to decodethe packet correctly (errors are commonly detected based on a CRC(Cyclic Redundancy Check)), the receiver requests a retransmission ofthe packet. Commonly the transmission of additional information iscalled “retransmission (of a packet)”, although this retransmission doesnot necessarily mean a transmission of the same encoded information, butcould also mean the transmission of any information belonging to thepacket (e.g. additional redundancy information).

Depending on the information (generally code-bits/symbols), of which thetransmission is composed of, and depending on how the receiver processesthe information, the following hybrid ARQ schemes are defined:

HARQ Type I

If the receiver fails to decode a packet correctly, the information ofthe encoded packet is discarded and a retransmission is requested. Thisimplies that all transmissions are decoded separately. Generally,retransmissions contain identical information (code-bits/symbols) to theinitial transmission.

HARQ Type II

If the receiver fails to decode a packet correctly, a retransmission isrequested, where the receiver stores the information of the (erroneousreceived) encoded packet as soft information (soft-bits/symbols). Thisimplies that a soft-buffer is required at the receiver. Retransmissionscan be composed out of identical, partly identical or non-identicalinformation (code-bits/symbols) according to the same packet as earliertransmissions.

When receiving a retransmission the receiver combines the storedinformation from the soft-buffer and the currently received informationand tries to decode the packet based on the combined information. Thereceiver may also try to decode the transmission individually, howevergenerally performance increases when combining transmissions.

The combining of transmissions refers to so-called soft-combining, wheremultiple received code-bits/symbols are likelihood combined and solelyreceived code-bits/symbols are code combined. Common methods forsoft-combining are Maximum Ratio Combining (MRC) of received modulationsymbols and log-likelihood-ratio (LLR) combining (LLR combing only worksfor code-bits).

Type II schemes are more sophisticated than Type I schemes, since theprobability for correct reception of a packet increases with receiveretransmissions. This increase comes at the cost of a required hybridARQ soft-buffer at the receiver. This scheme can be used to performdynamic link adaptation by controlling the amount of information to beretransmitted.

E.g. if the receiver detects that decoding has been “almost” successful,it can request only a small piece of information for the nextretransmission (smaller number of code-bits/symbols than in previoustransmission) to be transmitted. In this case it might happen that it iseven theoretically not possible to decode the packet correctly by onlyconsidering this retransmission by itself (non-self-decodableretransmissions).

HARQ Type III

This is a subset of Type II with the restriction that each transmissionmust be self-decodable.

Packet Scheduling

Packet scheduling may be a radio resource management algorithm used forallocating transmission opportunities and transmission formats to theusers admitted to a shared medium. Scheduling may be used in packetbased mobile radio networks in combination with adaptive modulation andcoding to maximize throughput/capacity by e.g. allocating transmissionopportunities to the users in favorable channel conditions. The packetdata service in UMTS may be applicable for the interactive andbackground traffic classes, though it may also be used for streamingservices. Traffic belonging to the interactive and background classes istreated as non real time (NRT) traffic and is controlled by the packetscheduler. The packet scheduling methodologies can be characterized by:

-   -   Scheduling period/frequency: The period over which users are        scheduled ahead in time.    -   Serve order: The order in which users are served, e.g. random        order (round robin) or according to channel quality (C/I or        throughput based).    -   Allocation method: The criterion for allocating resources, e.g.        same data amount or same power/code/time resources for all        queued users per allocation interval.

The packet scheduler for uplink is distributed between Radio NetworkController (RNC) and user equipment in 3GPP UMTS R99/R4/R5. On theuplink, the air interface resource to be shared by different users isthe total received power at a Node B, and consequently the task of thescheduler is to allocate the power among the user equipment(s). Incurrent UMTS R99/R4/R5 specifications the RNC controls the maximumrate/power a user equipment is allowed to transmit during uplinktransmission by allocating a set of different transport formats(modulation scheme, code rate, etc.) to each user equipment.

The establishment and reconfiguration of such a TFCS (transport formatcombination set) may be accomplished using Radio Resource Control (RRC)messaging between RNC and user equipment. The user equipment is allowedto autonomously choose among the allocated transport format combinationsbased on its own status e.g. available power and buffer status. Incurrent UMTS R99/R4/R5 specifications there is no control on timeimposed on the uplink user equipment transmissions. The scheduler maye.g. operate on transmission time interval basis.

UMTS Architecture

The high level R99/4/5 architecture of Universal MobileTelecommunication System (UMTS) is shown in FIG. 1 (see 3GPP TR 25.401:“UTRAN Overall Description”, available from http://www.3gpp.org). Thenetwork elements are functionally grouped into the Core Network (CN)101, the UMTS Terrestrial Radio Access Network (UTRAN) 102 and the UserEquipment (UE) 103. The UTRAN 102 is responsible for handling allradio-related functionality, while the CN 101 is responsible for routingcalls and data connections to external networks. The interconnections ofthese network elements are defined by open interfaces (Iu, Uu). Itshould be noted that UMTS system is modular and it is therefore possibleto have several network elements of the same type.

In the sequel two different architectures will be discussed. They aredefined with respect to logical distribution of functions across networkelements. In actual network deployment, each architecture may havedifferent physical realizations meaning that two or more networkelements may be combined into a single physical node.

FIG. 2 illustrates the current architecture of UTRAN. A number of RadioNetwork Controllers (RNCs) 201, 202 are connected to the CN 101. EachRNC 201, 202 controls one or several base stations (Node Bs) 203, 204,205, 206, which in turn communicate with the user equipments. An RNCcontrolling several base stations is called Controlling RNC (C-RNC) forthese base stations. A set of controlled base stations accompanied bytheir C-RNC is referred to as Radio Network Subsystem (RNS) 207, 208.For each connection between User Equipment and the UTRAN, one RNS is theServing RNS (S-RNS). It maintains the so-called Iu connection with theCore Network (CN) 101. When required, the Drift RNS 302 (D-RNS) 302supports the Serving RNS (S-RNS) 301 by providing radio resources asshown in FIG. 3. Respective RNCs are called Serving RNC (S-RNC) andDrift RNC (D-RNC). It is also possible and often the case that C-RNC andD-RNC are identical and therefore abbreviations S-RNC or RNC are used.

Mobility Management Within Rel99/4/5 UTRAN

Before explaining some procedures connected to mobility management, someterms frequently used in the following are defined first.

A radio link may be defined as a logical association between single UEand a single UTRAN access point. Its physical realization comprisesradio bearer transmissions.

A handover may be understood as a transfer of a UE connection from oneradio bearer to another (hard handover) with a temporary break inconnection or inclusion/exclusion of a radio bearer to/from UEconnection so that UE is constantly connected UTRAN (soft handover).Soft handover is specific for networks employing Code Division MultipleAccess (CDMA) technology. Handover execution may controlled by S-RNC inthe mobile radio network when taking the present UTRAN architecture asan example.

The active set associated to a UE comprises a set of radio linkssimultaneously involved in a specific communication service between UEand radio network. An active set update procedure may be employed tomodify the active set of the communication between UE and UTRAN, forexample during soft-handover. The procedure may comprise threefunctions: radio link addition, radio link removal and combined radiolink addition and removal. The maximum number of simultaneous radiolinks is set to eight. New radio links are added to the active set oncethe pilot signal strengths of respective base stations exceed certainthreshold relative to the pilot signal of the strongest member withinactive set.

A radio link is removed from the active set once the pilot signalstrength of the respective base station exceeds certain thresholdrelative to the strongest member of the active set. Threshold for radiolink addition is typically chosen to be higher than that for the radiolink deletion. Hence, addition and removal events form a hysteresis withrespect to pilot signal strengths.

Pilot signal measurements may be reported to the network (e.g. to S-RNC)from UE by means of RRC signaling. Before sending measurement results,some filtering is usually performed to average out the fast fading.Typical filtering duration may be about 200 ms contributing to handoverdelay. Based on measurement results, the network (e.g. S-RNC) may decideto trigger the execution of one of the functions of active set updateprocedure (addition/removal of a Node B to/from current Active Set).

Enhanced Uplink Dedicated Channel (E-DCH)

Uplink enhancements for Dedicated Transport Channels (DTCH) arecurrently studied by the 3GPP Technical Specification Group RAN (see3GPP TR 25.896: “Feasibility Study for Enhanced Uplink for UTRA FDD(Release 6)”, available at http://www.3gpp.org). Since the use ofIP-based services become more important, there is an increasing demandto improve the coverage and throughput of the RAN as well as to reducethe delay of the uplink dedicated transport channels. Streaming,interactive and background services could benefit from this enhanceduplink.

One enhancement is the usage of adaptive modulation and coding schemes(AMC) in connection with Node B controlled scheduling, thus anenhancement of the Uu interface. In the existing R99/R4/R5 system theuplink maximum data rate control resides in the RNC. By relocating thescheduler in the Node B the latency introduced due to signaling on theinterface between RNC and Node B may be reduced and thus the schedulermay be able to respond faster to temporal changes in the uplink load.This may reduce the overall latency in communications of the userequipment with the RAN. Therefore Node B controlled scheduling iscapable of better controlling the uplink interference and smoothing thenoise rise variance by allocating higher data rates quickly when theuplink load decreases and respectively by restricting the uplink datarates when the uplink load increases. The coverage and cell throughputmay be improved by a better control of the uplink interference.

Another technique, which may be considered to reduce the delay on theuplink, is introducing a shorter TTI (Transmission Time Interval) lengthfor the E-DCH compared to other transport channels. A transmission timeinterval length of 2 ms is currently investigated for use on the E-DCH,while a transmission time interval of 10 ms is commonly used on theother channels. Hybrid ARQ, which was one of the key technologies inHSDPA, is also considered for the enhanced uplink dedicated channel. TheHybrid ARQ protocol between a Node B and a user equipment allows forrapid retransmissions of erroneously received data units, and may thusreduce the number of RLC (Radio Link Control) retransmissions and theassociated delays. This may improve the quality of service experiencedby the end user.

To support enhancements described above, a new MAC sub-layer isintroduced which will be called MAC-e in the following (see 3GPP TSG RANWG1, meeting #31, Tdoc R01-030284, “Scheduled and Autonomous ModeOperation for the Enhanced Uplink”). The entities of this new sub-layer,which will be described in more detail in the following sections, may belocated in user equipment and Node B. On user equipment side, the MAC-eperforms the new task of multiplexing upper layer data (e.g. MAC-d) datainto the new enhanced transport channels and operating HARQ protocoltransmitting entities.

Further, the MAC-e sub-layer may be terminated in the S-RNC duringhandover at the UTRAN side. Thus, the reordering buffer for thereordering functionality provided may also reside in the S-RNC.

E-DCH MAC Architecture—UE Side

FIG. 4 shows the exemplary overall E-DCH MAC architecture on UE side. Anew MAC functional entity, the MAC-e/es, is added to the MACarchitecture of Release '99.

The MAC interworking on the UE side is illustrated in FIG. 5. There areM different data flows (MAC-d) carrying data packets from differentapplications to be transmitted from UE to Node B. These data flows canhave different QoS requirements (e.g. delay and error requirements) andmay require different configuration of HARQ instances. Each MAC-d flowrepresents a logical unit to which specific physical channel (e.g. gainfactor) and HARQ (e.g. maximum number of retransmissions) attributes canbe assigned.

Further, MAC-d multiplexing is supported for an E-DCH, i.e. severallogical channels with different priorities may be multiplexed onto thesame MAC-d flow. Data of multiple MAC-d flows can be multiplexed in oneMAC-e PDU. In the MAC-e header, the DDI (Data Description Indicator)field identifies logical channel, MAC-d flow and MAC-d PDU size. Amapping table is signalled over RRC, to allow the UE to set DDI values.The N field indicates the number of consecutive MAC-d PDUs correspondingto the same DDI value.

The MAC-e/es entity is depicted in more detail in FIG. 6. The MAC-es/ehandles the E-DCH specific functions. The selection of an appropriatetransport format for the transmission of data on E-DCH is done in theE-TFC Selection entity, which represents a function entity. Thetransport format selection is done according to the schedulinginformation (Relative Grants and Absolute Grants) received from UTRANvia L1, the available transmit power, priorities, e.g. logical channelpriorities. The HARQ entity handles the retransmission functionality forthe user. One HARQ entity supports multiple HARQ processes. The HARQentity handles all HARQ related functionalities required. Themultiplexing entity is responsible for concatenating multiple MAC-d PDUsinto MAC-es PDUs, and to multiplex one or multiple MAC-es PDUs into asingle MAC-e PDU, to be transmitted at the next TTI, and as instructedby the E-TFC selection function. It is also responsible for managing andsetting the TSN per logical channel for each MAC-es PDU. The MAC-e/esentity receives scheduling information from Node B (network side) viaLayer 1 signaling as shown in FIG. 6. Absolute grants are received onE-AGCH (Enhanced Absolute Grant Channel), relative grants are receivedon the E-RGCH (Enhanced Relative Grant Channel).

E-DCH MAC Architecture—UTRAN Side

An exemplary overall UTRAN MAC architecture is shown in FIG. 7. TheUTRAN MAC architecture includes a MAC-e entity and a MAC-es entity. Foreach UE that uses an E-DCH, one MAC-e entity per Node-B and one MAC-esentity in the S-RNC are configured. The MAC-e entity is located in theNode B and controls access to the E-DCH. Further, the MAC-e entity isconnected to MAC-es located in the S-RNC.

In FIG. 8 the MAC-e entity in Node B is depicted in more detail. Thereis one MAC-e entity in Node B for each UE and one E-DCH schedulerfunction in the Node-B for all UEs. The MAC-e entity and E-DCH schedulerhandle HSUPA (High-Speed Uplink Packet Access) specific functions inNode B. The E-DCH scheduling entity manages E-DCH cell resources betweenUEs. Commonly, scheduling assignments are determined and transmittedbased on scheduling requests from the UEs. The De-multiplexing entity inthe MAC-e entity provides de-multiplexing of MAC-e PDUs. MAC-es PDUs arethen forwarded to the MAC-es entity in the S-RNC.

One HARQ entity is capable of supporting multiple instances (HARQprocesses), e.g. employing a stop and wait HARQ protocols. Each HARQprocess is assigned a certain amount of the soft buffer memory forcombining the bits of the packets from outstanding retransmissions.Furthermore each process is responsible for generating ACKs or NACKsindicating delivery status of E-DCH transmissions. The HARQ entityhandles all tasks that are required for the HARQ protocol.

In FIG. 9 the MAC-es entity in the S-RNC is shown. It comprises thereordering buffer which provides in-sequence delivery to RLC and handlesthe combining of data from different Node Bs in case of soft handover.The combining is referred to as Macro diversity selection combining.

It should be noted that the required soft buffer size depends on theused HARQ scheme, e.g. an HARQ scheme using incremental redundancy (IR)requires more soft buffer than one with chase combining (CC).

E-DCH—Node B Controlled Scheduling

Node B controlled scheduling is one of the technical features for E-DCHwhich may enable more efficient use of the uplink resources in order toprovide a higher cell throughput in the uplink and may increase thecoverage. The term “Node B controlled scheduling” denotes thepossibility for a Node B to control uplink resources, e.g. theE-DPDCH/DPCCH power ratio, which the UE may use for uplink transmissionson the E-DCH within limits set by the S-RNC. Node B controlledscheduling is based on uplink and downlink control signaling togetherwith a set of rules on how the UE should behave with respect to thissignaling.

In the downlink, a resource indication (scheduling grant) is required toindicate to the UE the (maximum) amount of uplink resources it may use.When issuing scheduling grants, the Node B may use QoS-relatedinformation provided by the S-RNC and from the UE in the schedulingrequests to determine the appropriate allocation of resources forservicing the UE at the requested QoS parameters.

For the UMTS E-DCH, there are commonly two different UE scheduling modesdefined depending on the type of scheduling grants used. In thefollowing the characteristics of the scheduling grants are described.

Scheduling Grants

Scheduling grants are signaled in the downlink in order to indicate the(maximum) resource the UE may use for uplink transmissions. The grantsaffect the selection of a suitable transport format (TF) for thetransmission on the E-DCH (E-TFC selection). However, they usually donot influence the TFC selection (Transport Format Combination) forlegacy dedicated channels.

There are commonly two types of scheduling grants which are used for theNode B controlled scheduling:

-   -   absolute grants (AGs), and    -   relative grants (RGs)

The absolute grants provide an absolute limitation of the maximum amountof uplink resources the UE is allowed to use for uplink transmissions.Absolute grants are especially suitable to rapidly change the allocatedUL resources.

Relative grants are transmitted every TTI (Transmission Time Interval).They may be used to adapt the allocated uplink resources indicated byabsolute grants by granular adjustments: A relative grant indicates theUE to increase or decrease the previously allowed maximum uplinkresources by a certain offset (step).

Absolute grants are only signaled from the E-DCH serving cell. Relativegrants can be signaled from the serving cell as well as from anon-serving cell. The E-DCH serving cell denotes the entity (e.g. NodeB) actively allocating uplink resources to UEs controlled by thisserving cell, whereas a non-serving cell can only limit the allocateduplink resources, set by the serving cell. Each UE has only one servingcell.

Absolute grants may be valid for a single UE. An absolute grant validfor a single UE is referred to in the following as a “dedicated grant.Alternatively, an absolute grant may also be valid for a group of or allUEs within a cell. An absolute grant valid for a group of or all UEswill be referred to as a “common grant” in the following. The UE doesnot distinguish between common and dedicated grants.

Relative grants can be sent from serving cell as well as from anon-serving cell as already mentioned before. A relative grant signaledfrom the serving cell may indicate one of the three values, “UP”, “HOLD”and “DOWN”. “UP” respectively “DOWN” indicates the increase/decrease ofthe previously maximum used uplink resources (maximum power ratio) byone step. Relative grants from a non-serving cell can either signal a“HOLD” or “DOWN” command to the UE. As mentioned before relative grantsfrom non-serving cells can only limit the uplink resources set by theserving cell (overload indicator) but can not increase the resourcesthat can be used by a UE.

UE Scheduling Operation

Two different UE scheduling mode operations are defined for E-DCH, “RG”based and “non-RG” based mode of operation.

In the RG based mode, the UE obeys relative grants from the E-DCHserving cell. The RG based scheduling mode is also often referred to asthe dedicated rate control mode, because the scheduling grants usuallyaddress a single UE in the most cases.

In the following the UE behavior in this RG based scheduling mode isdescribed. The UE maintains a serving grant (SG) for each HARQ process.The serving grant indicates the maximum power ratio (E-DPDCH/DPCCH) theUE is allowed to use for transmissions on the E-DCH and is for theselection of an appropriate TFC during E-TFC selection. The servinggrant is updated by the scheduling grants signaled fromserving/non-serving cells. When the UE receives an absolute grant fromthe serving cell the serving grant is set to the power ratio signaled inthe absolute grant. The absolute grant can be valid for each HARQprocess or only for one HARQ process.

When no absolute grant is received from the serving cell the UE shouldfollow the relative grants from the serving cell, which are signaledevery TTI. A serving relative grant is interpreted relative to the UEpower ratio in the previous TTI for the same hybrid ARQ process as thetransmission, which the relative grant will affect. FIG. 10 illustratesthe timing relation for relative grants. In FIG. 10 it is assumed forexemplary purposes that there are four HARQ processes. The relativegrant received by the UE, which affects the serving grant of the firstHARQ process, is relative to the first HARQ process of the previous TTI(reference process).

The UE behavior in accordance to serving E-DCH relative grants is shownin the following:

-   -   When the UE receives an “UP” command from Serving E-DCH Radio        Link Set (RLS):        New SG _(i)=Last used power ratio (i)+Delta;    -   When the UE receives a “DOWN” command from Serving E-DCH RLS:        New SG _(i)=Last used power ratio (i)−Delta;

The “UP” and “DOWN” command is relative to the power ratio used forE-DCH transmission in the reference HARQ process. The new serving grantof the HARQ process j, affected by the relative grant, is an increaserespectively decrease of the last used power ratio in the reference HARQprocess.

The “HOLD” command indicates either that the SG of HARQ process jremains unchanged or that the SG of the reference HARQ process in theimmediate preceding TTI is reused for the current TTI for all HARQprocesses.

As already mentioned before a Node B from a non-serving RLS is onlyallowed to send relative grants, which can either indicate a “HOLD” or“DOWN”. The “DOWN” command enables non-serving cells to limit theintercell-interference caused by UEs which are in SHO with thesenon-serving cells. The UE behavior upon reception of non-servingrelative grants is as follows:

-   -   When the UE receives a “DOWN” from at least one Non-serving        E-DCH RLS:        For all HARQ processes (for all i): new SG _(i)=Last used power        ratio (i)−Delta

Relative grants from a non-serving RLS affect all HARQ processes in theUE. The amount of the reduction of the used power ratio might be staticor depending on the bit rate, for higher bit rates there might be alarger step size (Delta).

Next, the non-RG based scheduling mode will be outlined in furtherdetail. In case that there are relative grant channels (E-RGCH)established from the serving E-DCH RLS, the UE follows the non-RG basedmode of operation. The non-RG based scheduling mode is also referred toas common rate control mode.

The idea is to serve a group of or all UEs in the cell by commonabsolute grants. The common rate control has the advantage overdedicated rate control scheduling that less downlink signaling fromserving RLS perspective is needed, only common absolute grants and alsono relative grants.

However the use of common absolute grants to schedule an entire cellinevitably leads to a need for caution when new UEs start to transmit.If an absolute grant is issued with e.g. 64 kbps, hardware and RoT (Riseover Thermal) resources cannot be reserved for all UEs connected in thecell. Therefore when a new UE becomes active, it needs to starttransmissions at a low power ratio (i.e. using a low amount of uplinkresources) to enable dynamic allocation of hardware and RoT resources bythe Node B. This process is called UE ramping in the following: the UEautonomously ramps up its resource usage towards the maximum resourcesindicated by the latest absolute grant. The step sizes of the UE rampingare for example configured by RRC (Radio Resource Control).

The UE acts upon the absolute grant from serving RLS as follows:

-   -   The UE maintains a “serving grant” (SG), which is used in the        E-TFC selection algorithm as the maximum allowed E-DPDCH/DPCCH        power ratio for the uplink transmissions on the HARQ process it        refers to    -   The UE furthermore maintains a “maximum serving grant” (MAX SG)        which is set to the last received absolute grant for all HARQ        processes    -   If the UE has data to transmit and the SG is below the MAX SG,        the SG is increased over time by configurable steps (autonomous        ramp-up) until SG is equal to MAX SG    -   If the SG is above the MAX SG (due to reception of a new        absolute grant lowering the MAX SG), then the SG is immediately        set equal to MAX SG    -   If the UE transmitted at a given power ratio below the current        SG for more than n TTIs (where n is a configurable parameter        that can be set to an infinite value), then the SG is set equal        to this given power ratio. This in effect forces the UE to use        autonomous ramp-up after some continuous activity below SG.

The UE ramps up towards the last received absolute grant for example atthe beginning of a connection and after some certain period of time(Δt), during which the UE is transmitting with a lower power ratio thanallocated by serving cell.

The relative grants from non-serving RLS affect the MAX SG of a UE.

-   -   When the UE receives a “DOWN” from at least one Non-serving        E-DCH RLS new MAX SG=MAX SG−Delta

The difference of the UE behavior for the non-RG based scheduling modecompared to the RG based scheduling mode with respect to relative grantsfrom a non-serving RLS is that the relative grants affect the MAX SGinstead of the last used power ratio. Therefore the UE is still allowedto ramp-up to the reduced MAX SG. When no more “DOWN” commands from anon-serving RLS is received the UE sets the MAX SG to the last receivedabsolute grant and ramps towards this MAX SG.

An exemplary scenario for the non-RG based mode is shown in FIG. 11. TheUE is in soft handover and transmits the uplink data in four HARQprocesses, numbered 1, 2, 3 and 4 to a serving cell and a non-servingcell. Upon starting communication, MAX SG is equal to AG, and SG isincreased step-wise until reaching MAX SG.

Upon reaching MAX SG, the non-serving cell sends a “DOWN” command to theUE in order to request same to reduce the uplink resources utilized. TheUE sets the new MAX SG equal to AG minus a configurable delta, andtransmits the next uplink data for processes 1 to 4 with this reducedMAX SG value (i.e. MAX SG=SG). Upon expiry of a predetermined timeperiod (Δt) the MAX SG is reset to AG. Again, the non-serving cellrequests a reduction of the utilized uplink resources and the UE reactsupon the further “DOWN” commands from the non-serving cell as explainedabove.

Rate Request Signaling

In order to enable Node B to schedule efficiently while considering alsothe QoS requirements of a service mapped on the E-DCH, an UE providesthe Node B information on its QoS requirements by means of rate requestsignaling.

There are two kinds of rate request signaling information on the uplink:the so called “happy bit”, which is a flag related to a rate request onthe E-DPCCH and the scheduling information (SI), which is commonly sentin-band on the E-DCH.

From a system point of view, the one-bit rate request may beadvantageously used by the serving cell to effect small adjustments inthe resource allocation for example by means of relative grants. On thecontrary, scheduling information may advantageously be employed formaking longer term scheduling decisions, which would be reflected in thetransmission of an absolute grant. Details on the two rate requestsignaling methods are provided in the following.

Scheduling Information Sent on E-DCH

As mentioned before the scheduling information should provide Node Binformation on the UE status in order to allow for an efficientscheduling. Scheduling information may be included in the header of aMAC-e PDU. The information is commonly sent periodically to Node B inorder to allow the Node B to keep track of the UE status. E.g. thescheduling information comprises following information fields:

-   -   Logical channel ID of the highest priority data in the        scheduling information    -   UE buffer occupancy (in Bytes)        -   Buffer status for the highest priority logical channel with            data in buffer        -   Total buffer status    -   Power status information        -   Estimation of the available power ratio versus DPCCH (taking            into account HS-DPCCH). UE should not take power of DCHs            into account when performing the estimation

Identifying the logical channel by the logical channel ID from which thehighest priority data originates may enable the Node B to determine theQoS requirements, e.g. the corresponding MAC-d flow power offset,logical channel priority or GBR (Guaranteed Bit Rate) attribute, of thisparticular logical channel. This in turn enables the Node B to determinethe next scheduling grant message required to transmit the data In theUE buffer, which allows for a more precise grant allocation. In additionto the highest priority data buffer status, it may be beneficial for theNode B to have some information on the total buffer status. Thisinformation may help in making decisions on the “long-term” resourceallocation.

In order for the serving Node B to be able to allocate uplink resourceseffectively, it needs to know up to what power each UE is able totransmit. This information could be conveyed in the form of a “powerheadroom” measurement, indicating how much power the UE has left over ontop of that what is used for DPCCH transmissions (power status). Thepower status report could also be used for the triggering of a TTIreconfiguration, e.g. switching between 2 ms and 10 ms TTI and viceversa.

Happy Bit

As already explained above the happy bit denotes a one-bit rate requestrelated flag, which is sent on the E-DPCCH. The “happy bit” indicateswhether the respective UE is “happy” or “unhappy” with the currentserving grant (SG).

The UE indicates that it is “unhappy”, if both of the following criteriaare met:

-   -   Power status criterion: UE has power available to send at higher        data rates (E-TFCS) and    -   Buffer occupancy criterion: Total buffer status would require        more than n TTIs with the current Grants (where n is        configurable).

Otherwise, the UE indicates that it is “happy” with the current servinggrant.

As described above serving and non-serving RLS may control the maximumserving grant by means of scheduling grants in the non-RG basedscheduling mode. The maximum serving grant in the UE is set to the lastreceived absolute grant from serving RLS, a “DOWN” command from anon-serving RLS decreases the maximum serving grant by one step. In casea “DOWN” command is received while UE is ramping up and the servinggrant is below the maximum serving grant, the UE is still allowed toramp up to the new MAX SG=MAX SG−Delta.

Moreover, as has been outlined, the happy/unhappy status of the UEbasically indicates to the serving cell, whether the UE is capable oftransmitting with a higher data rate respectively higher power ratiothan currently allowed by the serving grant. Essentially the happy bitprovides the serving cell with some information on the power and bufferstatus of the respective UE. The Node B scheduler may adjust the alloweduplink resources for example by a particular UE by relative grants inresponse to the happy-bit set by the UE.

Next, the RG based scheduling mode is referred to. Table 1 below showssome exemplary scenarios of the power headroom available to a UE, itsbuffer status, the setting of the happy-bit according to these twoparameters and the scheduling command that should be sent next by theNode B controlling the serving cell on the E-RGCH (E-DCH Relative GrantChannel). Power Case headroom Buffer status Happy bit E-RGCH 1 + +Unhappy Up 2 + − Happy Keep 3 − + Happy Keep 4 − − Happy Keep

“+/−” for power headroom corresponds to the case when UE has more/lessavailable power than allowed by the serving grant. “+/−” for the bufferstatus corresponds to the case when buffered data requires more/lessthan n TTIs for its transmission at the allowed serving grant. Uponreceiving the happy bit, Node B scheduler determines the relative grant,which is sent on the E-RGCH. In case the UE is unhappy and there areuplink resources available serving cell could up-rate the UE by an “UP”command, as shown in case 1.

By considering the received E-TFC on the E-DPDCH together with the“happy bit”, the serving cell can determine when a “DOWN” command hasbeen sent from non-serving RLS. In case the UE indicates “unhappy” buttransmits in the same TTI with less power than actually granted by theserving grants, the serving cell can recognize that a “DOWN” command hasbeen signaled from a non-serving RLS. This situation is shown in Table 2below (case 4). power power limited Buffer Happy E- E- Case headroom bystatus bit TFC RGCH 1 + Serving Node B + UH MAX Up 2 − UE + H LESS Keep3 − UE − H LESS Keep 4 + Non-Serving + UH LESS Keep Node B

By taking the happy/unhappy status of the UE and the received E-TFC intoaccount the serving cell can distinguish between case 1 and case 4 andhence detect “DOWN” commands from a non-serving RLS. The possibility todetect a “DOWN” command from a non-Serving Node B enables the servingRLS to react appropriately, for example by restricting the data rate ofUEs in soft handover between the serving cell and the non-serving cellthat has sent the “DOWN” command.

For the non-RG based scheduling mode, the situation is different.Scheduling grants from serving/non-serving RLS control the maximumserving grant of a UE—in contrast to the RG based scheduling mode, wherethe serving grant is controlled by scheduling grants. However thedefinition of the happy bit is based on the serving grant and not on themaximum serving grant used in the non-RG scheduling mode. During theramping procedure the serving grant is below the maximum serving grant.When UE is ramping up towards the maximum serving grant it can transmitwith a higher power (i.e. “higher” E-TFC) than allowed by the currentserving grant. Therefore according to the criteria of the unhappy statusdefined previously, the UE would indicate “unhappy” to the serving cell.However this behavior would not reflect the real situation, because theUE is allowed to transmit with higher power than the current servinggrant: it is basically allowed to ramp up the power ration for E-DCHtransmission autonomously up to the maximum serving grant.

One further important drawback with this behavior would be that servingcell cannot distinguish anymore whether a “DOWN” command from anon-serving RLS has been sent limiting the maximum uplink data rate of aUE or the fact that the UE is currently ramping up towards maximumserving grant. Therefore, the serving cell may no longer takeappropriate countermeasures when non-serving Node Bs send “DOWN”commands.

SUMMARY OF THE INVENTION

The object of the invention is to provide new criteria for setting thehappy bit. A further aim is to enable the Node B of the serving cell todetect “DOWN” commands from other non-serving cells during softhandover.

The object is solved by the subject matter of the independent claims.Advantageous embodiments of the invention are subject matters to thedependent claims.

One of the main aspects of the invention is the definition of newcriteria for setting the happy bit. In contrast to the conventionalcriteria, a mobile terminal is only allowed to set the happy bit to“unhappy”, i.e. may only request additional uplink resources by settingthe bit, if the mobile terminal is not ramping its uplink resourceutilization. Hence, only if the mobile terminal utilizes the maximumuplink resources granted by the serving cell, the mobile terminal mayindicate an “unhappy” status. Another effect achieved by this definitionof criteria for setting the “unhappy” bit is that serving cell iscapable of detecting during handover, if a non-serving cell in themobile terminal's active set during soft handover has indicated toreduce the uplink resource utilization.

According to an advantageous embodiment, a method for communicatingresource requests for dedicated uplink channel resources in a mobilecommunication system is provided. According to this method, the mobileterminal transmits uplink data to a base station via a dedicated uplinkchannel at a transmission power utilizing a corresponding amount ofuplink resources per transmission time interval and uplink controlinformation associated to the uplink data transmitted within atransmission time interval via a dedicated uplink control channel to thebase station. Further, the mobile terminal receives a scheduling grantsetting the maximum amount of uplink resources the mobile terminal isallowed to utilize for the transmission of uplink data via the uplinkdedicated channel within a transmission time interval from the basestation controlling the serving cell.

If the amount of uplink resources utilized for uplink data transmissionis lower than the maximum amount of uplink resources, the mobileterminal may increase the amount of uplink resources utilized for uplinkdata transmissions via the dedicated uplink channel step-wise until theutilized amount of uplink resources is equivalent to the maximum amountof uplink resources.

The control information transmitted by the mobile terminal comprises aresource request flag that, when set, requests the base stationcontrolling the serving cell to increase the uplink resources for uplinkdata transmissions via the uplink dedicated channel. The mobile terminalmay not set the resource request flag, if the mobile terminal transmitsuplink data via the dedicated uplink channel not utilizing the maximumamount of uplink resources set by a scheduling grant and if the mobileterminal is in a process of step-wise increasing the amount of uplinkresources utilized for uplink data transmissions.

In a further embodiment of the invention, the mobile terminal mayfurther determine the occupancy of a buffer in the mobile terminal. Thebuffer buffers data to be transmitted via the dedicated uplink channel.The mobile terminal sets the resource request flag to request the basestation to increase the uplink resources for uplink data transmissionsvia the uplink dedicated channel,

-   a) if the power status of the mobile terminal allows for uplink data    transmission via the dedicated uplink channel utilizing more uplink    resources than the maximum uplink resources set by the scheduling    grant of the base station controlling the serving cell,-   b) and if the maximum uplink resources set by the scheduling grant    from the base station controlling the serving cell require more than    a configurable number of transmission time intervals for    transmitting buffered uplink data via the dedicated uplink channel,-   c) and if the mobile terminal is currently utilizing the maximum    uplink resources set by the scheduling grant for uplink data    transmission.

According to another embodiment of the invention, the scheduling grantindicates the maximum uplink resources all mobile terminals controlledby the base station of the serving cell transmitting data via adedicated uplink channel respectively are allowed to utilize for uplinkdata transmissions via the uplink dedicated channels within atransmission time interval.

Another advantageous embodiment relates to situations in which themobile terminal is in soft handover between the serving cell controlledby the base station and a non-serving cell controlled by a base station.In this embodiment, the mobile terminal may further transmit the uplinkdata via a dedicated uplink channel to the base station controlling thenon-serving cell, and may set the maximum uplink resources the mobileterminal is allowed to utilize for uplink data transmissions via bothdedicated uplink channels according to the scheduling grant receivedfrom the base station controlling the serving cell.

In a variation of this embodiment of the invention, the mobile terminalmay further receive a relative scheduling grant from the base stationcontrolling the non-serving cell indicating to decrease the amount ofuplink resources currently utilized by the mobile terminal. The mobileterminal may decrease the amount of uplink resources currently utilizedby the mobile terminal in response to the relative scheduling grant, andmay set the maximum amount of uplink resources to a decreased amount ofuplink resources for uplink data transmission in the next transmissiontime interval.

In a further variation of this embodiment of the invention, the mobileterminal further sets the resource request flag to request the basestation to increase the uplink resources for uplink data transmissionsvia the uplink dedicated channel,

-   a) if the power status of the mobile terminal allows for uplink data    transmission via the dedicated uplink channel utilizing more uplink    resources than the maximum uplink resources set by scheduling grants    from the serving cell and/or the non-serving cell,-   b) and if the maximum uplink resources set by the scheduling grants    requires more than a configurable number of transmission time    intervals for transmitting buffered uplink data via the dedicated    uplink channel,-   c) and if the mobile terminal is currently utilizing the maximum    uplink resources set by the scheduling grants for uplink data    transmission.

In another variation of the embodiment, the control informationtransmitted via the dedicated control channel to the base stationcontrolling the serving cell further comprises a transport formatindicator indicating the transport format combination used fortransmitting uplink data to the base station controlling the servingcell within a transmission time interval. The transport format indicatorindicates a transport format combination utilizing a lower amount ofuplink resources than allowed by the base station of the serving cell inthe scheduling grant. If the mobile terminal is transmitting uplink datavia the uplink dedicated channel to the base station controlling theserving cell utilizing the decreased amount of uplink resources, it mayset the resource request flag in the control information transmitted inthe transmission time interval to the base station controlling theserving cell.

This combination of the transport format indicator and the resourcerequest flag in the control information indicates to the base stationcontrolling the serving cell that the maximum amount of uplink resourceshas been decreased based on a relative scheduling grant received fromthe base station controlling the non-serving cell.

In a further embodiment, the step size when step-wise increasing theamount of uplink resources is configurable. For example, the mobileterminal may receive control information via higher layer signalingindicating the step size to use and may set the step size according tothe control information.

In a variation of this embodiment of the invention, the controlinformation indicating the step size may set the step size to a valueequal to the difference between the maximum amount of resources themobile terminal is allowed to utilize and the amount of uplink resourcescurrently utilized by the mobile terminal.

Another embodiment of the invention relates to a mobile terminalcommunicating resource requests for dedicated uplink channel resourcesin a mobile communication system. The mobile terminal may comprise atransmitter for transmitting uplink data to a base station via adedicated uplink channel at a transmission power utilizing acorresponding amount of uplink resources per transmission time interval,and for transmitting uplink control information associated to the uplinkdata transmitted within a transmission time interval via a dedicateduplink control channel to the base station.

The mobile terminal may further comprise a receiver for receiving ascheduling grant setting the maximum amount of uplink resources themobile terminal is allowed to utilize for the transmission of uplinkdata via the uplink dedicated channel within a transmission timeinterval from the base station controlling the serving cell, and aprocessing means for step-wise increasing the amount of uplink resourcesutilized for uplink data transmissions via the dedicated uplink channeluntil the utilized amount of uplink resources is equivalent to themaximum amount of uplink resources, if the amount of uplink resourcesutilized for uplink data transmission is lower than the maximum amountof uplink resources

According to this embodiment, the control information comprises aresource request flag that, when set, requests the base stationcontrolling the serving cell to increase the uplink resources for uplinkdata transmissions via the uplink dedicated channel. The mobile terminalis adapted to not set the resource request flag, if the mobile terminaltransmits uplink data via the dedicated uplink channel without utilizingthe maximum amount of uplink resources set by a scheduling grant and ifthe mobile terminal is in a process of step-wise Increasing the amountof uplink resources utilized for uplink data transmissions.

A further embodiment of the invention relates to the mobile terminalcomprising means adapted to perform the steps of the method according toone of the different embodiments and variations thereof above.

Further another embodiment of the invention provides a computer readablemedium storing instructions that, when executed by a processor of amobile terminal, cause the mobile terminal to communicate resourcerequests for dedicated uplink channel resources in a mobilecommunication system. The mobile terminal is caused to communicateresource requests by transmitting uplink data to a base station via adedicated uplink channel at a transmission power utilizing acorresponding amount of uplink resources per transmission time interval,transmitting uplink control information associated to the uplink datatransmitted within a transmission time interval via a dedicated uplinkcontrol channel to the base station, receiving a scheduling grantsetting the maximum amount of uplink resources the mobile terminal isallowed to utilize for the transmission of uplink data via the uplinkdedicated channel within a transmission time interval from the basestation controlling the serving cell, and step-wise increasing theamount of uplink resources utilized for uplink data transmissions viathe dedicated uplink channel until the utilized amount of uplinkresources is equivalent to the maximum amount of uplink resources, ifthe amount of uplink resources utilized for uplink data transmission islower than the maximum amount of uplink resources.

The control information comprises a resource request flag that, whenset, requests the base station controlling the serving cell to increasethe uplink resources for uplink data transmissions via the uplinkdedicated channel. Moreover, the instructions cause the mobile terminalto not set the resource request flag, if the mobile terminal transmitsuplink data via the dedicated uplink channel not utilizing the maximumamount of uplink resources set by a scheduling grant and if the mobileterminal is in a process of step-wise increasing the amount of uplinkresources utilized for uplink data transmissions.

Another embodiment of the invention relates to a computer readablemedium storing instructions that, when executed by the processor of themobile terminal cause the mobile terminal to perform the steps of themethod according to one the various embodiments and variations thereofdescribed herein.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows the high-level architecture of UMTS,

FIG. 2 shows the architecture of the UTRAN according to UMTS R99/4/5,

FIG. 3 shows a Drift and a Serving Radio Subsystem,

FIG. 4 shows the overall E-DCH MAC architecture at a user equipment,

FIG. 5 shows the MAC interworking in a simplified architecture at a userequipment,

FIG. 6 shows the MAC-e/es architecture at a user equipment,

FIG. 7 shows an overall MAC architecture in the UTRAN,

FIG. 8 shows the MAC-e architecture at a Node B,

FIG. 9 shows the MAC-es architecture at a S-RNC,

FIG. 10 shows the timing relation of relative grant,

FIG. 11 shows the non-RG mode operation of a UE,

FIG. 12 shows a flow chart of the operation of a mobile terminalaccording to an exemplary embodiment of the invention, and

FIG. 13 shows a modified non-RG mode operation of a mobile terminalaccording to an exemplary embodiment of the Invention.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to a UMTS communication system and the terminologyused in the subsequent sections mainly relates to the UMTS terminology.However, the used terminology and the description of the embodimentswith respect to a UMTS architecture is not intended to limit theprinciples and ideas of the inventions to such systems.

Also the detailed explanations given in the Technical Background sectionabove are merely intended to better understand the mostly UMTS specificexemplary embodiments described in the following and should not beunderstood as limiting the invention to the described specificimplementations of processes and functions in the mobile communicationnetwork.

As has been explained above, the current specified criteria for theunhappy status of a UE does not enable Node B to detect “DOWN” commandsfrom a non-serving RLS in the non-RG based mode of operation. This inturn makes it impossible for the serving cell to take appropriatemeasures in order to handle or prevent further overload situations in anon-serving RLS.

One of the main ideas of the invention is therefore a new definition ofthe criteria for the unhappy status of a UE. According to this mainidea, the mobile terminal may not indicate an “unhappy” condition aslong as it is ramping up its resource utilization towards the maximumamount resources it is allowed to utilize for data transmissions on adedicated uplink channel. The new definition of the unhappy statusprovided by the invention allows the Node B of the serving cell todetect “DOWN” commands from non-serving cells, if the mobile terminal isin soft handover.

Since the serving grant (SG) in a UE is only different to the maximumserving grant (MAX SG) while UE is in the ramping procedure, i.e. isincreasing the utilized uplink resources towards maximum serving grant,according to one embodiment, the UE is always “happy” while ramping upresources. Thus, during the ramping procedure, the UE will not set theunhappy bit. After the ramping procedure has been finished the servinggrant is equal to maximum serving grant.

In case the power and buffer status of the UE allows the transmissionwith a higher power ratio respectively E-TFC than allowed by maximumserving grant, the UE may indicate “unhappy” to serving cell. By thisdefinition serving cell would be also able to detect a “DOWN” commandfrom a non-serving RLS, which is shown in the following table. PW BufferCase headroom PW limited by status Happy bit E-TFC 1 + Ramping + happyLESS procedure SG < MAX SG 2 + Non-serving RLS + unhappy LESS MAX SG <AG (SG = MAX SG)

A possible definition of the unhappy criteria of a UE would be thefollowing:

According to an embodiment of the invention, the UE thus indicates thatit is “unhappy” with the current scheduling grants from the serving cell(and the non-serving cell(s) for the in a soft handover scenario), ifall of the following criteria are met:

-   -   UE has power available to send at higher data rates (E-TFCs)    -   Total buffer status would require more than n TTIs with the        current grants (where n is configurable)    -   UE is transmitting with MAX SG (SG=MAX SG)

It is important to notice that while ramping, the UE will not set thehappy bit to indicate an “unhappy” condition. In other words, the UEwill not request the serving cell's Node B to increase resources foruplink transmissions via the dedicated uplink channel while it isincreasing the utilized uplink resources towards the maximum servinggrant.

In the following an embodiment of the invention will be explained withreference to FIG. 12 showing a flow chart illustrating the operation ofa mobile terminal when communicating on a dedicated uplink channel, suchas an E-DCH.

The mobile terminal maintains a state variable for every HARQ process,which indicates the amount of resources the mobile terminal is using fordata transmissions on a dedicated uplink channel. Taking again an UMTSsystem as an example, the state variable may be used in the E-TFCselection algorithm as the maximum allowed E-DPDCH/DPCCH power ratio forthe transmission of the HARQ process it refers to. This state variablemay be referred to as a serving grant (SG).

The maximum serving grant (MAX SG) is another state variable for eachHARQ process that denotes the maximum amount of uplink resources themobile terminal may use for data transmissions on the uplink channel.Taking the example of transmissions via an UMTS E-DCH again, this statevariable may define the maximum allowed E-DPDCH/DPCCH ratio.

According to this embodiment the maximum serving grant is controlled bythe scheduling grants from serving cell. When the mobile terminal is insoft handover, i.e. is connected to a serving cell an at least onefurther non-serving cell, the maximum serving grant may be controlled bythe serving cell and the non-serving cell.

Upon starting uplink data transmission, the mobile terminal initializes1201 the serving grant value. As outlined previously, the currentserving grant value indicates to the E-TFC selection entity, which powerratio can be used for the selection of an E-TFC for data transmission onthe E-DCH when considering a UMTS system for exemplary purposes.

Further, the mobile terminal determines 1202 whether an absolute granthas been received through the serving cell, i.e. from the Node B of theserving cell responsible for scheduling the respective UE. According tothis exemplary embodiment, the non-RG scheduling case is considered,i.e. the UE is only provided with absolute grants from the serving cell.These scheduling grants set the amount of resources the UE us allowed toutilize for the transmission of uplink data. When considering again theexample of E-DCH transmissions, the absolute grants indicate theE-DPDCH/DPCCH power ratio.

In an alternative embodiment of the invention, the serving cell may useboth, absolute grants and relative grants to specify the maximum servinggrant, i.e. the maximum amount of resources the UE is allowed to utilizefor uplink data transmissions on the uplink channel. In anotheralternative embodiment of the invention, the serving cell schedules allor a group of UEs in the cell, i.e. transmits common grants to the UEs.

If the mobile terminal has received an absolute grant, which has not yetbeen considered, the mobile terminal sets 1203 the maximum serving grantto the value indicated by the absolute grant from the serving cell.

Next, the mobile terminal determines 1204, whether the serving grant maybe increased by the step size delta₁ without exceeding the maximumserving grant. If this is the case, the mobile terminal ramps up 1205the current serving grant value, i.e. increases the serving grant valueby a configurable step (delta₁):SG=SG+delta₁.

Otherwise, the mobile terminal sets 1206 the serving grant value to themaximum serving grant value.

With respect to steps 1204, 1205 and 1206, it should be noted that in analternative embodiments of the invention, the step size (delta₁) mayvary from between successive increments of the serving grant value. Forexample, in the first iteration the serving grant may be increased bydelta₁, in the second iteration by 2-delta₁, etc. until the maximumserving grant value is reached. Another alternative may be to choose thestep size delta₁ such that it equals the difference between the currentmaximum serving grant and the current serving grant value.

The step size delta₁ can be preconfigured or may be set by controlsignaling associated to the uplink transmissions on the dedicated uplinkchannel received through RRC signaling.

Next, the steps 1207, 1208 and 1209 are discussed. These steps areoptional and may only be performed when the mobile terminal is in softhandover. In this situation, the mobile terminal determines 1207 whethera relative grant indicating a “DOWN” command has been received from anon-serving cell. As previously discussed a grant from a non-servingcell indicates to the mobile terminal to reduce its uplink resourceutlization by a configurable amount.

If a relative grant has been received, the mobile terminal sets 1208 themaximum serving grant to the current last used power ratio (PR) valueminus the configurable step-size (delta₁):MAX SG=last used power ratio−delta₂and sets 1209 the serving grant value to be used for E-TFC selection fordata transmission in the next TTI to the new maximum serving grantvalue. In this embodiment, the power ratio may be considered as ameasure of the uplink resources utilized for data transmission on thededicated uplink channel.

According to another embodiment of the invention, the mobile terminaldoes not reset the maximum serving grant value to that indicated in thelast absolute grant received, but keeps the maximum serving grant valueuntil receiving a new absolute grant from the serving cell.

It should be noted that the step size delta₂ may be individually set bymeans of control signaling from the serving cell and/or non-servingcell(s) or may be preconfigured. Moreover, it is not necessary thatdelta, and delta₂ are of equal values.

In the exemplary embodiment of the invention illustrated in FIG. 12, therelative grants of the non-serving cell(s) dominate the absolute grantsin that the relative grants “overwrite” the maximum serving grant valuein case a absolute and a relative grant have been received. Thisoperation may be advantageous, as this operation may allow forcontrolling the noise rise in the non-serving cell(s) during handover.

However, it may also be advantageous to allow the absolute grantsdominating the relative grants, if both have been received before a nextE-TFC selection process. For this situation, essentially, steps 1207,1208 and 1209 would need to be performed prior to steps 1202 to 1206.

Either way, upon having updated the serving grant value and the maximumserving grant value—if necessary—the mobile terminal decides 1210whether the happy bit (resource request flag) for requesting more uplinkresources should be set. As explained previously, the mobile terminal isprohibited from setting the happy bit to indicate an “unhappy”condition, as long as the mobile terminal is ramping up resourceutilization, i.e. the current serving grant is lower than the maximumserving grant and is (successively) increased as explained above. Themobile terminal may only indicate an “unhappy” condition, if the mobileterminal is currently using the maximum allowed resources fortransmission of uplink data.

As indicated previously, the mobile terminal not being in soft handovermay only indicate and “unhappy” condition by setting the happy bit:

-   -   if the power status of the mobile terminal allows for uplink        data transmission via the dedicated uplink channel utilizing        more uplink resources than the maximum uplink resources (MAX SG)        set by the scheduling grant of the base station controlling the        serving cell,    -   and if the maximum uplink resources (MAX SG) set by the        scheduling grant from the base station controlling the serving        cell require more than a configurable number of transmission        time intervals for transmitting buffered uplink data via the        dedicated uplink channel,    -   and if the mobile terminal is currently utilizing the maximum        uplink resources (MAX SG=SG) set by the scheduling grant for        uplink data transmission.

If the mobile terminal is in soft handover, these criteria may beredefined. In the soft handover case, the mobile terminal may set theresource request flag, i.e. indicate an “unhappy” condition

-   -   if the power status of the mobile terminal allows for uplink        data transmission via the dedicated uplink channel utilizing        more uplink resources than the maximum uplink resources (MAX SG)        set by scheduling grants from the serving cell and/or the        non-serving cell,    -   and if the maximum uplink resources (MAX SG) set by the        scheduling grants require more than a configurable number of        transmission time intervals for transmitting buffered uplink        data via the dedicated uplink channel,    -   and if the mobile terminal is currently utilizing the maximum        uplink resources (MAX SG=SG) set by the scheduling grants for        uplink data transmission.

Upon having decided whether to request more uplink resources by settingthe happy bit, the mobile terminal next selects 1211 a transport formatcombination (TFC) for the current serving grant value. The E-TFCselection may for example be based on logical channel priorities like inthe UMTS Release '99, i.e. the UE shall maximize the transmission ofhigher priority data.

Upon having selected the appropriate E-TFC for the transmission of theuplink data via the dedicated uplink channel, the data is transmitted1212 along with control information associated thereto. The controlinformation Inter alia comprise the happy bit (resource request flag) aswell as a transport format combination indicator (TFCI) indicating theTFC used for transmitting the uplink data in the current TTI.Considering the example of an E-DCH uplink channel again, the uplinkdata are transmitted via and E-DPDCH (Enhanced Dedicated Physical DataCHannel). The control information is transmitted via the E-DPCCH(Enhanced Dedicated Physical Control CHannel) which is a physicalchannel used to transmit control information associated with the E-DCH.

In the soft handover case, the combination of the happy bit and the TFCIenables the Node B controlling the serving cell to recognize whether themobile terminal has received a “DOWN” command from a non-serving cell.If the mobile terminal is ramping up its resource utilization for uplinktransmissions, it is prohibited from setting the happy bit to indicatean “unhappy” condition. At the same time the TFCI will indicate aresource utilization lower than that granted by the serving cell. Hence,the Node B of the serving cells may derive from this combination of theTFCI and the happy bit that the mobile terminal is Increasing itsresource utilization.

When receiving a “DOWN” command from a non-serving cell, the mobileterminal will set its resource utilization according tonew serving grant=new maximum serving grant=previous used powerratio−delta₂as explained previously. Given, that the buffer status requires and thepower status allows for the utilization of more uplink resources, themobile terminal will set the happy bit to indicate an “unhappy”condition. Again, the TFCI will indicate to the Node B controlling theserving cell that the resource utilization is below that granted by theNode B. Thus, the Node B may detect based on this combination that themobile terminal has received a “DOWN” command from a non-serving cell.

The happy bit setting according to an embodiment of the invention willbe explained with reference to FIG. 13. FIG. 13 illustrates therelations between the current serving grant, the maximum serving grantand the happy bit status in accordance with an exemplary embodiment ofthe invention.

For the uplink communication of a mobile terminal in soft handover viatwo dedicated uplink channels the presence of four HARQ processes(shaded rectangles numbered 1 to 4) is assumed. At the beginning of thecommunication the terminal receives an absolute grant AG from theserving cell and sets the maximum serving grant accordingly. First, themobile terminal ramps up its resource utilization by increasing theserving grant step-wise (phase #1). Accordingly the happy bit does notrequest for more uplink resources (happy condition).

Next, the mobile terminal receives a “DOWN” command from a non-servingcell. The maximum serving grant is set to the previous serving grantminus a configurable offset as described above, and the mobile terminalreduces its resource utilization to the new maximum serving grant set(phase #2). The mobile terminal sets the happy bit in the controlinformation to indicate that it requires more resources to transmituplink data. Further, the control information indicate that the resourceutilization for the data transmissions in phase #2 is below theresources granted by the absolute grant from the serving cell.

The Node B controlling the serving cell detects based on the combinationof the happy bit and the TFCI that the mobile terminal has received a“DOWN” command and reacts by sending a new absolute grant. In responseto the reception of the new absolute grant, the mobile terminal startsramping up resource utilization again and indicates a happy condition(phase #3). In phase #4, the serving grant is equal to the new maximumserving grant set by the last absolute grant from the serving cell.Assuming that all conditions outlined above are fulfilled, the mobileterminal indicates an unhappy condition. As the TCFI indicates resourceutilization equal to the one set by the last absolute grant, the Node Bcontrolling the serving cell may derive from the control informationthat the mobile terminal has finished the ramping and requests moreresources for uplink transmissions.

Further, the mobile terminal receives another “DOWN” command from thenon-serving cell. As in phase #2, the mobile terminal will thus reducethe resource utilization in phase #5 and indicates unhappy condition.The Node B controlling the serving cell may again detect the receptionof a “DOWN” command from a non-serving cell based on the signaledcontrol information, but does not decide to alter resource utilizationgranted previously.

The embodiments of the invention described above have been mainlyrelated to the non-RG based scheduling mode. However the principlesoutlined above and in particular the definition of the criteria forsetting the happy bit may be equally applied to the RG based schedulingmode.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various above mentioned methods as well as thevarious logical blocks, modules, circuits described above may beimplemented or performed using computing devices (processors), as forexample general purpose processors, digital signal processors (DSP),application specific integrated, circuits (ASIC), field programmablegate arrays (FPGA) or other programmable logic devices, etc. The variousembodiments of the invention may also be performed or embodied by acombination of these devices.

Further, the various embodiments of the invention may also beimplemented by means of software modules which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware Implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

1. A method for communicating resource requests for dedicated uplinkchannel resources in a mobile communication system, comprisingperforming by the mobile terminal: transmitting via a dedicated uplinkcontrol channel uplink control information associated to uplink data toa base station controlling a serving cell, wherein the controlinformation comprises a resource request flag that, when set, requeststhe base station to increase uplink resources for uplink datatransmissions via an uplink dedicated channel, and wherein the mobileterminal does set the resource request flag, if the mobile terminaltransmits uplink data via the dedicated uplink channel utilizing themaximum amount of uplink resources set by a scheduling grant.
 2. Amethod for communicating resource requests for dedicated uplink channelresources in a mobile communication system, comprising performing by themobile terminal: transmitting via a dedicated uplink control channeluplink control information associated to uplink data to a base stationcontrolling a serving cell, wherein the control information comprises aresource request flag that, when set, requests the base station toincrease uplink resources for uplink data transmissions via an uplinkdedicated channel, and wherein the mobile terminal does not set theresource request flag, if the mobile terminal transmits uplink data viathe dedicated uplink channel without utilizing the maximum amount ofuplink resources set by a scheduling grant or the mobile terminal is ina process of step-wise increasing the amount of uplink resourcesutilized for uplink data transmissions.
 3. The method according to claim1, further comprising: receiving a scheduling grant setting the maximumamount of uplink resources the mobile terminal is allowed to utilize forthe transmission of uplink data via the uplink dedicated channel fromthe base station controlling the serving cell, and if the amount ofuplink resources utilized for uplink data transmission is lower than themaximum amount of uplink resources, step-wise increasing the amount ofuplink resources utilized for uplink data transmissions via thededicated uplink channel until the utilized amount of uplink resourcesis equivalent to the maximum amount of uplink resources.
 4. The methodaccording to claim 1, further comprising: determining the occupancy of abuffer in the mobile terminal buffering data to be transmitted via thededicated uplink channel, and setting the resource request flag torequest the base station to increase the uplink resources for uplinkdata transmissions via the uplink dedicated channel, if all of thefollowing criteria are met: a) the power status of the mobile terminalallows for uplink data transmission via the dedicated uplink channelutilizing more uplink resources than the maximum uplink resources set bythe scheduling grant of the base station controlling the serving cell,b) the maximum uplink resources set by the scheduling grant from thebase station controlling the serving cell require more than aconfigurable number of transmission time intervals for transmittingbuffered uplink data via the dedicated uplink channel, and c) the mobileterminal is currently utilizing the maximum uplink resources set by thescheduling grant for uplink data transmission.
 5. The method accordingto claim 1, wherein the scheduling grant indicates the maximum uplinkresources all mobile terminals controlled by the base station of theserving cell transmitting data via a dedicated uplink channelrespectively are allowed to utilize for uplink data transmissions viathe uplink dedicated channels within a transmission time interval. 6.The method according to claim 2, wherein the mobile terminal is in softhandover between a serving cell controlled by the base station and anon-serving cell controlled by a base station, and wherein the methodfurther comprises: transmitting the uplink data via a dedicated uplinkchannel to the base station controlling the non-serving cell, andsetting the maximum uplink resources the mobile terminal is allowed toutilize for uplink data transmissions via both dedicated uplink channelsaccording to the scheduling grant received from the base stationcontrolling the serving cell.
 7. The method according to claim 6,further comprising: receiving a relative scheduling grant from the basestation controlling the non-serving cell indicating to decrease theamount of uplink resources currently utilized by the mobile terminal,decreasing the amount of uplink resources currently utilized by themobile terminal in response to the relative scheduling grant, andsetting the maximum amount of uplink resources to a decreased amount ofuplink resources for uplink data transmission in the next transmissiontime interval.
 8. The method according to claim 7, wherein the mobileterminal sets the resource request flag to request the base station toincrease the uplink resources for uplink data transmissions via theuplink dedicated channel, if all of the following criteria are met: a)the power status of the mobile terminal allows for uplink datatransmission via the dedicated uplink channel utilizing more uplinkresources than the maximum uplink resources set by scheduling grantsfrom the serving cell and/or the non-serving cell, b) the maximum uplinkresources set by the scheduling grants requires more than a configurablenumber of transmission time intervals for transmitting buffered uplinkdata via the dedicated uplink channel, and c) the mobile terminal iscurrently utilizing the maximum uplink resources set by the schedulinggrants for uplink data transmission.
 9. The method according to claim 7,wherein the control information transmitted via the dedicated controlchannel to the base station controlling the serving cell furthercomprises a transport format indicator indicating the transport formatcombination used for transmitting uplink data to the base stationcontrolling the serving cell within a transmission time interval,wherein the transport format indicator indicates a transport formatcombination utilizing a lower amount of uplink resources than allowed bythe base station of the serving cell in the scheduling grant, and if themobile terminal is transmitting uplink data via the uplink dedicatedchannel to the base station controlling the serving cell utilizing thedecreased amount of uplink resources, setting the resource request flagin the control information transmitted in the transmission time intervalto the base station controlling the serving cell, wherein thecombination of the transport format indicator and the resource requestflag in the control information indicates to the base stationcontrolling the serving cell that the maximum amount of uplink resourceshas been decreased based on a relative scheduling grant received fromthe base station controlling the non-serving cell.
 10. The methodaccording to claim 1, wherein the step size when step-wise increasingthe amount of uplink resources is configurable.
 11. The method accordingto claim 10, further comprising the steps of receiving controlinformation indicating the step size, and setting the step sizeaccording to the control information.
 12. The method according to claim11, wherein control information indicating the step size set the stepsize to a value equal to the difference between the maximum amount ofresources the mobile terminal is allowed to utilize and the amount ofuplink resources currently utilized by the mobile terminal.
 13. A mobileterminal for communicating resource requests for dedicated uplinkchannel resources in a mobile communication system comprising: atransmitter operable to transmit via a dedicated uplink control channeluplink control information associated to uplink data to a base stationcontrolling a serving cell, wherein the control information comprises aresource request flag that, when set, requests the base stationcontrolling the serving cell to increase uplink resources for uplinkdata transmissions via an uplink dedicated channel, and wherein themobile terminal is operable to set the resource request flag, if themobile terminal transmits uplink data via the dedicated uplink channelutilizing the maximum amount of uplink resources set by a schedulinggrant.
 14. A mobile terminal for communicating resource requests fordedicated uplink channel resources in a mobile communication systemcomprising: a transmitter operable to transmit via a dedicated uplinkcontrol channel uplink control information associated to uplink data toa base station, wherein the control information comprises a resourcerequest flag that, when set, requests the base station controlling theserving cell to increase uplink resources for uplink data transmissionsvia an uplink dedicated channel, and wherein the mobile terminal isoperable to not set the resource request flag, if the mobile terminaltransmits uplink data via the dedicated uplink channel without utilizingthe maximum amount of uplink resources set by a scheduling grant or themobile terminal is in a process of step-wise increasing the amount ofuplink resources utilized for uplink data transmissions.
 15. The mobileterminal according to claim 13, further comprising: a receiver operableto receive a scheduling grant setting the maximum amount of uplinkresources the mobile terminal is allowed to utilize for the transmissionof uplink data via the uplink dedicated channel from the base stationcontrolling the serving cell, a processing section operable to step-wiseincrease the amount of uplink resources utilized for uplink datatransmissions via the dedicated uplink channel until the utilized amountof uplink resources is equivalent to the maximum amount of uplinkresources, if the amount of uplink resources utilized for uplink datatransmission is lower than the maximum amount of uplink resources. 16.(canceled)
 17. A computer readable medium storing instructions that,when executed by a processor of a mobile terminal, cause the mobileterminal to communicate resource requests for dedicated uplink channelresources in a mobile communication system, by: transmitting via adedicated uplink control channel uplink control information associatedto uplink data to a base station, wherein the control informationcomprises a resource request flag that, when set, requests the basestation controlling the serving cell to increase the uplink resourcesfor uplink data transmissions via an uplink dedicated channel, andwherein the instruction cause the mobile terminal to set the resourcerequest flag, if the mobile terminal transmits uplink data via thededicated uplink channel utilizing the maximum amount of uplinkresources set by a scheduling grant.
 18. A computer readable mediumstoring instructions that, when executed by a processor of a mobileterminal, cause the mobile terminal to communicate resource requests fordedicated uplink channel resources in a mobile communication system, by:transmitting via a dedicated uplink control channel uplink controlinformation associated to uplink data to a base station, wherein thecontrol information comprises a resource request flag that, when set,requests the base station controlling the serving cell to increase theuplink resources for uplink data transmissions via an uplink dedicatedchannel, and wherein the instruction cause the mobile terminal to notset the resource request flag, if the mobile terminal transmits uplinkdata via the dedicated uplink channel without utilizing the maximumamount of uplink resources set by a scheduling grant or the mobileterminal is in a process of step-wise increasing the amount of uplinkresources utilized for uplink data transmissions.
 19. (canceled)
 20. Themethod according to claim 2, further comprising: receiving a schedulinggrant setting the maximum amount of uplink resources the mobile terminalis allowed to utilize for the transmission of uplink data via the uplinkdedicated channel from the base station controlling the serving cell,and if the amount of uplink resources utilized for uplink datatransmission is lower than the maximum amount of uplink resources,step-wise increasing the amount of uplink resources utilized for uplinkdata transmissions via the dedicated uplink channel until the utilizedamount of uplink resources is equivalent to the maximum amount of uplinkresources.
 21. The method according to claim 2, further comprising:determining the occupancy of a buffer in the mobile terminal bufferingdata to be transmitted via the dedicated uplink channel, and setting theresource request flag to request the base station to increase the uplinkresources for uplink data transmissions via the uplink dedicatedchannel, if all of the following criteria are met: a) the power statusof the mobile terminal allows for uplink data transmission via thededicated uplink channel utilizing more uplink resources than themaximum uplink resources set by the scheduling grant of the base stationcontrolling the serving cell, b) the maximum uplink resources set by thescheduling grant from the base station controlling the serving cellrequire more than a configurable number of transmission time intervalsfor transmitting buffered uplink data via the dedicated uplink channel,and c) the mobile terminal is currently utilizing the maximum uplinkresources set by the scheduling grant for uplink data transmission. 22.The method according to claim 2, wherein the scheduling grant indicatesthe maximum uplink resources all mobile terminals controlled by the basestation of the serving cell transmitting data via a dedicated uplinkchannel respectively are allowed to utilize for uplink datatransmissions via the uplink dedicated channels within a transmissiontime interval.
 23. The method according to claim 7, wherein the controlinformation transmitted via the dedicated control channel to the basestation controlling the serving cell further comprises a transportformat indicator indicating the transport format combination used fortransmitting uplink data to the base station controlling the servingcell within a transmission time interval, wherein the transport formatindicator indicates a transport format combination utilizing a loweramount of uplink resources than allowed by the base station of theserving cell in the scheduling grant, and if the mobile terminal istransmitting uplink data via the uplink dedicated channel to the basestation controlling the serving cell utilizing the decreased amount ofuplink resources, setting the resource request flag in the controlinformation transmitted in the transmission time interval to the basestation controlling the serving cell, wherein the combination of thetransport format indicator and the resource request flag in the controlinformation indicates to the base station controlling the serving cellthat the maximum amount of uplink resources has been decreased based ona relative scheduling grant received from the base station controllingthe non-serving cell.
 24. The method according to claim 1, wherein thestep size when step-wise increasing the amount of uplink resources isconfigurable.
 25. The mobile terminal according to claim 13, furthercomprising: a receiver operable to receive a scheduling grant settingthe maximum amount of uplink resources the mobile terminal is allowed toutilize for the transmission of uplink data via the uplink dedicatedchannel from the base station controlling the serving cell, a processingsection operable to step-wise increase the amount of uplink resourcesutilized for uplink data transmissions via the dedicated uplink channeluntil the utilized amount of uplink resources is equivalent to themaximum amount of uplink resources, if the amount of uplink resourcesutilized for uplink data transmission is lower than the maximum amountof uplink resources.